/// <remarks>
/// This method implements best type inference for the conditional operator ?:.
/// NOTE: If either expression is an error type, we return error type as the inference result.
/// </remarks>
public static TypeSymbol InferBestTypeForConditionalOperator(BoundExpression expr1, BoundExpression expr2, Conversions conversions, out bool hadMultipleCandidates, ref HashSet <DiagnosticInfo> useSiteDiagnostics)
{
// SPEC: The second and third operands, x and y, of the ?: operator control the type of the conditional expression.
// SPEC: • If x has type X and y has type Y then
// SPEC: o If an implicit conversion (§6.1) exists from X to Y, but not from Y to X, then Y is the type of the conditional expression.
// SPEC: o If an implicit conversion (§6.1) exists from Y to X, but not from X to Y, then X is the type of the conditional expression.
// SPEC: o Otherwise, no expression type can be determined, and a compile-time error occurs.
// SPEC: • If only one of x and y has a type, and both x and y, are implicitly convertible to that type, then that is the type of the conditional expression.
// SPEC: • Otherwise, no expression type can be determined, and a compile-time error occurs.
// A type is a candidate if all expressions are convertible to that type.
ArrayBuilder <TypeSymbol> candidateTypes = ArrayBuilder <TypeSymbol> .GetInstance();
TypeSymbol type1 = expr1.Type;
if ((object)type1 != null)
{
if (type1.IsErrorType())
{
candidateTypes.Free();
hadMultipleCandidates = false;
return(type1);
}
if (conversions.ClassifyImplicitConversionFromExpression(expr2, type1, ref useSiteDiagnostics).Exists)
{
candidateTypes.Add(type1);
}
}
TypeSymbol type2 = expr2.Type;
if ((object)type2 != null && type2 != type1)
{
if (type2.IsErrorType())
{
candidateTypes.Free();
hadMultipleCandidates = false;
return(type2);
}
if (conversions.ClassifyImplicitConversionFromExpression(expr1, type2, ref useSiteDiagnostics).Exists)
{
candidateTypes.Add(type2);
}
}
hadMultipleCandidates = candidateTypes.Count > 1;
return(InferBestType(candidateTypes.ToImmutableAndFree(), conversions, ref useSiteDiagnostics));
}
/// <remarks>
/// This method implements best type inference for the conditional operator ?:.
/// NOTE: If either expression is an error type, we return error type as the inference result.
/// </remarks>
public static TypeSymbol InferBestTypeForConditionalOperator(BoundExpression expr1, BoundExpression expr2, Conversions conversions, out bool hadMultipleCandidates, ref HashSet<DiagnosticInfo> useSiteDiagnostics)
{
// SPEC: The second and third operands, x and y, of the ?: operator control the type of the conditional expression.
// SPEC: • If x has type X and y has type Y then
// SPEC: o If an implicit conversion (§6.1) exists from X to Y, but not from Y to X, then Y is the type of the conditional expression.
// SPEC: o If an implicit conversion (§6.1) exists from Y to X, but not from X to Y, then X is the type of the conditional expression.
// SPEC: o Otherwise, no expression type can be determined, and a compile-time error occurs.
// SPEC: • If only one of x and y has a type, and both x and y, are implicitly convertible to that type, then that is the type of the conditional expression.
// SPEC: • Otherwise, no expression type can be determined, and a compile-time error occurs.
// A type is a candidate if all expressions are convertible to that type.
ArrayBuilder<TypeSymbol> candidateTypes = ArrayBuilder<TypeSymbol>.GetInstance();
TypeSymbol type1 = expr1.Type;
if ((object)type1 != null)
{
if (type1.IsErrorType())
{
candidateTypes.Free();
hadMultipleCandidates = false;
return type1;
}
if (conversions.ClassifyImplicitConversionFromExpression(expr2, type1, ref useSiteDiagnostics).Exists)
{
candidateTypes.Add(type1);
}
}
TypeSymbol type2 = expr2.Type;
if ((object)type2 != null && type2 != type1)
{
if (type2.IsErrorType())
{
candidateTypes.Free();
hadMultipleCandidates = false;
return type2;
}
if (conversions.ClassifyImplicitConversionFromExpression(expr1, type2, ref useSiteDiagnostics).Exists)
{
candidateTypes.Add(type2);
}
}
hadMultipleCandidates = candidateTypes.Count > 1;
return InferBestType(candidateTypes.ToImmutableAndFree(), conversions, ref useSiteDiagnostics);
}
